JPH11354297A - Plasma generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid a fluctuation in a deposited layer on the basis of generation of an alternating magnetic field in a microwave. SOLUTION: A single rod-shaped conductor 4 is guided by penetrating through a vacuum chamber 3 on the inside of a single insulating tube 5, an inside diameter of the insulating tube 5 is formed larger than a diameter of the conductor 4, the insulating tube 5 is held by a wall 6 of the vacuum chamber 3 at least in one end part, the outside surface of the insulating tube 5 is sealed to the wall, the conductor 4 is connected to a first source 8 for generating an alternating magnetic field at least in one end part, a range of the part where the rod- shaped conductor 4 extends by rushing in the vacuum chamber 3 is molded as a spiral body 2, and here, the winding length L of the part is set to L=C/cos (α) in a wave length λo=10 deg.<α<15 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an alternating electromagnetic field (el
ektromagnetisch. Wechself
apparatus for generating a plasma in a vacuum chamber by using at least one rod-like conductor, wherein the at least one rod-shaped conductor protrudes into the vacuum chamber inside an insulating tube made of an insulating material; Is formed larger than the diameter of the conductor, the insulating tube at least at one end,
Of the type in which it is held on the wall of a vacuum chamber, the outer surface of the insulating tube is sealed against the wall, and the conductor is connected at least at one end to a source for generating an alternating electromagnetic field. About things.

[0002]

2. Description of the Related Art A known device for generating a plasma (DE 19503205).
It is possible to generate a plasma for surface treatment and coating technology in a limited operating area (process area, gas pressure, microwave power). This known device mainly consists of a cylindrical glass tube provided in a vacuum process chamber and a metal conductive tube provided in the glass tube. Atmospheric pressure is formed. Microwave power is introduced through the walls of the vacuum process chamber by two feeds on both sides and two coaxial lines made of metal consisting of an inner conductor and an outer conductor. There is no outer conductor of the coaxial line inside the vacuum process chamber, and the outer conductor is replaced by plasma discharge. This plasma discharge is ignited and maintained by the microwave output under sufficient ignition conditions (gas pressure). in this case,
The microwave output can enter the vacuum process chamber from the two metal coaxial lines through the glass tube. The plasma surrounds the cylindrical glass tube from the outside and, together with the inner conductor, forms one coaxial line with a very high attenuation coating. With stationary microwave power supplied on both sides, the gas pressure in the vacuum process chamber is uniform, apparently along the device, where the plasma is apparent where the outer conductor of the coaxial line is absent inside the vacuum process chamber Can be adjusted to

Furthermore, a device is known for locally generating plasma in a processing chamber by means of microwave excitation (DE-A 41 36 297). This known device is divided into an outer part and an inner part by a wall-mountable flange or the wall itself, in which case a microwave generator is arranged on the outer part. The microwaves of this microwave generator are guided towards the inner part via a microwave input coupling device. The microwave incoupling device has an outer waveguide made of an insulating material, which penetrates the flange, and has an inner conductor made of metal extending into the outer waveguide. , Microwaves are coupled into the inner conductor from the microwave generator.

Furthermore, a device has been proposed for generating a plasma in a vacuum chamber using an alternating electromagnetic field (DE-A-197 22 272.2). In this device, a rod-shaped conductor is guided through a vacuum chamber inside an insulating tube made of an insulating material, and the inner diameter of the insulating tube is formed larger than the diameter of the conductor. The insulating tube is held on the wall of the vacuum chamber at both ends,
The outer surface of the insulating tube is sealed against this wall and the conductors are connected at both ends respectively to a first source for generating an alternating electromagnetic field. The rod-shaped conductors are each surrounded at a small distance by a tube made of a conductive material in the direction of the middle part of the conductor in the region of the two-wall guides, in which case the two tubes are Concentrically arranged with respect to the insulating tube, an annular cylindrical intermediate chamber formed by the insulating tube and each tube piece, respectively, is connected to a second source for generating an alternating electromagnetic field. ing.

[0005]

SUMMARY OF THE INVENTION The object of the invention is to provide a device of the type mentioned at the outset which is suitable for avoiding fluctuations in the deposited layer due to the generation of an alternating magnetic field in the microwave. Device. The device should be more inexpensive to manufacture,
In particular, it is desirable to avoid the incorporation of costly isolators to protect the microwave transmitter from reflected output. That is, the antennas may also have the property of emitting high frequency microwaves without reabsorbing the power reflected by the application (eg, plasma), in addition to the radiation properties inherent to each antenna. It is desirable to be formed in.

[0006]

In order to solve this problem, according to the structure of the present invention, the region of the rod-shaped conductor that extends into the vacuum chamber and extends is formed as a spiral body. Is less than 10 ° <α <
At a helical winding angle of 15 °, it was made to substantially correspond to the wavelength λ.

[0007]

According to an advantageous embodiment of the invention, a plurality of rod-shaped conductors are guided through a vacuum chamber inside an insulating tube of insulating material, the inner diameter of which is reduced. ,
The insulating tube is formed larger than the diameter of the conductor, the insulating tube is held at both ends by the wall of the vacuum chamber, the outer surface of the insulating tube is sealed against the wall, and the conductor The area of the part of the rod-shaped conductor that extends into the vacuum chamber and extends into the vacuum chamber is shaped as a spiral, provided that the winding length of the two parts is This corresponds approximately to the wavelength λ and the helix angle of 10 ° <α <15 °.

In an alternative embodiment of the invention, a plurality of rod-shaped conductors are guided through a vacuum chamber inside a plurality of insulating tubes made of insulating material, the inner diameter of which is reduced. ,
Each of the conductors is formed to have a diameter larger than the diameter of the conductor, and each of the insulating tubes is held at one end by a wall of the vacuum chamber, and the outer surface of the insulating tube is sealed to the wall, and Are connected at one end to a source for generating an alternating electromagnetic field, respectively, and the area of the rod-shaped conductor, which extends into the vacuum chamber and extends, is formed as a spiral, The winding lengths of both parts approximately correspond to the wavelength λ and the helical winding angle of 10 ° <α <15 °.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

[0010] device shown in Figure 1, relates to helical antennas are operated by T ₁ mode. In this case, circularly polarized microwave radiation is emitted from the free end of the helix along the central axis to ignite and maintain the plasma discharge.

A microwave output is supplied from a microwave generator by a rectangular waveguide 10, and the microwave output is supplied to the coaxial line 4 by impedance matching elements 11 and 12.
Is transmitted to The helical body of the helical antenna 2 is connected to the inner conductor of the coaxial line 4, and the transverse electromagnetic wave of the coaxial line 4,
That is, the TEM waves are converted into circularly polarized waves, and the circularly polarized waves are radiated into the vacuum chamber 3 through the insulating tube 5 which is vacuum-tight but has microwave transparency. Metal conductivity of the vacuum chamber 3 (metal
isch leitend. The wall 6) serves as a reflector shield for the backward wave.

A plurality of devices of the above type emit microwave power in the same plasma processing chamber (FIG. 6). In this case, the individual helical antennas are separated by microwave technology, provided that the devices arranged opposite one another have to have opposite winding directions (helicity).

To be precise, if the device provided on one side has clockwise helicity, the other device must have counterclockwise helicity. Under ideal conditions, left circularly polarized microwave radiation cannot be absorbed by a clockwise helix or helical antenna, or conversely, right circularly polarized microwave radiation can be counterclockwise. It cannot be absorbed by helical or spiral antennas.
Circularly polarized microwave radiation changes the respective polarization direction upon reflection on a flat metal-conductive surface.

The two devices according to the invention, which are respectively situated opposite one another, can be arranged in a common vacuum-tight and microwave-permeable insulating tube 5 as shown in FIG. In this case, both devices have opposite helicities.

The microwave radiation emitted from the device according to the invention in the forward direction generates a plasma discharge which, for the microwave radiation, forms an absorbing dielectric in terms of wave dynamics, Microwaves undergo strong attenuation within this dielectric. In order to reduce the attenuation and thus change the geometry of the plasma (especially: stretching in the longitudinal direction), it may be advantageous to form a connection passage without plasma between the two devices. If the operating parameters are set appropriately, a closed plasma column with little standing wave magnetic field pattern can be formed between each two devices according to the invention arranged opposite each other. .

Used to radiate microwaves,
Helical shaped or helically shaped rod antenna (also called "helix") has a characteristic that is operated in the so-called "T ₁ mode". FIG.
Shows a spiral antenna or helix with about four turns. A microwave output is supplied to the spiral antenna via a coaxial line. The radiation properties of the "helix" relate firstly to the ratio of the winding diameter D to the wavelength of the supplied microwave λ ₀ , and secondly to the helical angle α. Depending on the setting of these parameters, a "helix" antenna can, in extreme cases,
As shown in FIGS. 4 and 5, radiation is emitted in two different modes exhibiting radiation characteristics that are sufficiently complementary to each other.

[0017] _{T 1} mode: winding length L = C / cos
(Α) substantially corresponds to the wavelength λ ₀ and 10 ° <α <15 °.

In this operating condition, the helix or spiral antenna radiates from the free end of the helix concentrically with respect to the helix center axis, with a significantly large main lobe and a small minor lobe, as shown in FIG. (Endfire or vertical antenna). Moreover, in a helical antenna with at least four turns, the radiation has a sufficient circular polarization, the direction of rotation of which is defined by the helicity of the antenna.
Such kind of helical antenna is referred to as "Claus coil (Kraus-Coil)" (monofilament, axial mode _{T 1 R} 1). The detailed configuration of the Claus coil is described in "Antennas", 2nd edition (John
D. By Kraus, publisher McGraw-Hill
Book Company, see Chapter 7). The possible antenna gain is related to the geometry of the helix, for example the winding diameter, the helix angle and the overall length, and may be up to 15 dB, but in this case
It is almost independent of the diameter of the tubular metallic conductive material and the diameter of its intrinsic electrical resistance (DT Emerso).
n "Radio Radio Astron"
omy Observatory "Antenna
Compendium Volume 4, pages 64 to 68,
1995, see publisher AARL).

[0019] _{T 0} mode: winding length L = C / cos
(Α) is significantly smaller than the wavelength λ ₀ and 10 ° <α <15 °.

In this operating state, the helix radiates in an intensity distribution having lobes extending substantially perpendicular to the helix center axis, as shown in FIG. 5, that is, lobes extending in the radial direction like a straight rod antenna. .
Such an operating state is the basis for the device described in DE-A-4136297 or DE-A-19503205. T ₀ mode is not important for the object of the present invention.

T ₂ , T ₃ ,. . . Mode: winding length L
= C / cos (α) is the wavelength λ ₀ and 10 ゜ <α <15
Significantly larger than ゜.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an apparatus including a spiral antenna and an insulating tube closed on the vacuum chamber side.

FIG. 2 is a schematic diagram of a typical spiral antenna.

FIG. 3 is a development view of a spiral antenna.

[4] The apparatus shown in FIG. 1 is a schematic view illustrating a plasma cloud when operated by T ₁ mode.

[5] The apparatus shown in FIG. 1 is a schematic view illustrating a plasma cloud during operation with a T ₀ mode.

FIG. 6 is a schematic diagram showing a plasma cloud in an embodiment using a device with two helical antennas, which are arranged opposite each other in a closed insulating tube;

FIG. 7 is a schematic diagram illustrating a plasma cloud in an embodiment using an apparatus with two helical antennas positioned opposite each other with a common insulating tube surrounding both helical antennas.

[Explanation of symbols]

2 spiral antenna, 3 vacuum chamber, 4 coaxial line,
5 Insulation tube, 6,7 wall, 8,9 source, 10 Rectangular waveguide, 11, 12 Impedance matching element, 1
3 spiral antenna, 14 insulating tube, 15 coaxial line, 16 insulating tube

Claims (3)

[Claims] In an apparatus for generating plasma in a vacuum chamber (3) using an alternating electromagnetic field, one rod-shaped conductor (4) is connected to one insulating tube (5) made of an insulating material. ) Is guided through the vacuum chamber (3),
The inside diameter of the insulating tube (5) is formed larger than the diameter of the conductor (4), and the insulating tube (5) is formed at least at one end on the wall (6, 7) of the vacuum chamber (3). Being held,
The outer surface of the insulating tube (5) is sealed against the wall (6, 7), and the conductor (4) is at least at one end and a first source (8; 9), the area of the rod-shaped conductor (4) extending into the vacuum chamber (3) extending into the vacuum chamber (3) is formed as a spiral body (2), provided that the winding length of this part is (L) is L = C / cos at a wavelength λ ₀ = 10 ° <α <15 °
(Α) An apparatus for generating plasma, characterized in that: 2. An apparatus for generating plasma in a vacuum chamber (3) by using an alternating electromagnetic field, wherein a plurality of rod-shaped conductors (4, 15) are made of one insulating tube made of an insulating material. It is guided through the vacuum chamber (3) inside (14), and the inside diameter of the insulating tube (14) is equal to that of the conductor (4, 15).
The insulating tube (14) is held at both ends by walls (6, 7) of the vacuum chamber (3), and the insulating tube (14) is The outer surface of (14) is sealed and the conductors (4, 15) are each connected to a unique source (8; 9) for generating an alternating electromagnetic field, and the rod-shaped conductors (4, 15) ), Vacuum chamber (3)
The area of the part that extends into and extends into the spiral (2; 13)
Wherein the winding length (L, L ') of the two portions is L = C / cos (α) at a wavelength λ ₀ = 10 ° <α <15 °. , A device for generating plasma. 3. An apparatus for generating plasma in a vacuum chamber (3) using an alternating electromagnetic field, wherein a plurality of rod-shaped conductors (4, 15) are formed of a plurality of insulating tubes made of an insulating material. (5, 16) are guided through the vacuum chamber (3), and the inner diameter of the insulating tubes (5, 16) is formed larger than the diameter of the conductor (4, 15), respectively.
Insulating tubes (5, 16) are held at one end on the walls (6, 7) of the vacuum chamber (3), respectively, against the walls (6, 7). ) Is sealed, and each conductor (4, 15) is connected at one end to a source (8; 9) for generating an alternating electromagnetic field, respectively, and a rod-shaped conductor (4, 15) is provided. , 15) extend into the vacuum chamber (3) by the spiral body (2;
13), wherein the winding length (L, L ') of the two parts is L = C / cos (α) at a wavelength λ ₀ = 10 ° <α <15 °. An apparatus for generating plasma.